Static electricity is an objective natural phenomenon, and has a variety of ways of production, such as contact, friction, and induction between electrical appliances. Static electricity is characterized by long-term accumulation, high voltage, low electric quantity, small current and short duration of action. Static electricity causes serious harm in a number of fields. Electrification by friction and human body static are two big hazards in the electronics industry, often resulting in unstable operation of electrical and electronic products, and even damage. ESD is an academic subject formed since the mid-20th century for studying generation, harm, protection and the like of static electricity, with the electrostatic protection equipment internationally customarily generally referred to as ESD.
For a product applied to power management, a self-protection solution is used as its electrostatic protection solution because of its large area, as shown in FIG. 1, i.e., the protected circuit itself has certain electrostatic discharge capability, needing no additional electrostatic protection measures. However, an ordinary device without targeted optimized structure has weak self-protection capability. If a traditional electrostatic protection structure is used for a power device, although ESD has enough protection capability, its area may be more than one time greater compared to an ordinary device, which is mainly because the distance L between the metal contact hole of the drain region or source region and the polysilicon gate is much greater compared to the ordinary device, with the size of L directly relating to the electrostatic protection capability of this device, the greater the L, the higher the electrostatic protection capability. For example, L is 0.5 μm for an ordinary device, while 2.5 μm and more for a traditional electrostatic protection structure.